Mounting for airplane engines



July 15, 1941. R, s. TROTT MOUNTING FOR AIRPLANE ENGINES Filed June 10,1938 4 Sheets-Sheet 1 INVESTOR July 15, 1941. R s, TROTT 2,249,194

MOUNTING FOR AIRPLANE ENGINES Filed June 10, 1938 4 Sheets-Sheet 2INVENTOR. FIG. |2., 3 imi w July 15, 1941. R, 8, mm 2,249,194

MOUNTING FOR AIRPLANE ENGINES Filed June 10, 1938 4 Sheets-Sheet 3 26 2/F IG. H. Llll lhLl mum V v INVENTOR. Hm. ||ml I July 15, 1941. R. s.TROTT MOUNTING FOR AIRPLANE ENGINES 4 Sheets-Sheet 4 Filed June 10, 1938IN VENTOR. W4 0% Patented July 15, 1941 MOUNTING Foa AIRPLANE ENGINESHolland 8. Trott, Denver, Colo. Application June 16, 1938, Serial No.212,887

4 Claims.

My invention relates to engine mountings. and especially to engine;mountings for radial enines used in airplanes.

The object of my invention is to provide a method of cushioning allengine unit forces, and

to provide an engine mounting which will carry out my method and cushionall engine unit forces, and thereby eliminate their transmission to theairplane.

A further object is to provide such an engine mounting which willcushion each of the main sets of forces of the engine unit, withoutcreating any new forces by such cushionings.

Further objects will appear during the following description.

A statement regarding engine unit forces in their relation to presentradial engine mountings will make an understanding of my inventioneasier to grasp.

In present radial engine mountings, the engine mountframework isattached to the fuselage of the airplane generally at four pointsimmediately in front of the firewall, and the engine is attached to thefront of this engine mount framework about two feet or more in front ofthe firewall, by about nine engine bolts on about a twenty-four inchbolt circle.

The four mounting bolts or pins on the firewall, sometimes have thinrubber bushings, and the engine bolts also may have circumferentiallyelongated rubber bushings.

But, regardless of these and other details, present radial enginemountings are so poor in their results, that the finger tips placedagainst any part of any airplane so far built, will, when the enginesare running, disclose that the plane is being vibrated by the engineforces.

Many flying men even seem to think that in an airplane engine vibrationis necessary, that it always has been present and always will bepresent.

There are at least four sets of engine unit forces which are at presentresponsible for the vibration of all planes.

These forces are as follows:

(1) The draft force, or the pull of the propeller; (2) the torque forceor reaction to the twisting of the propeller; (3) transverse forces, orforces in planes normal to the crankshaft axis, and which may be out ofbalance forces due to out of balance in the propeller or other movingparts, or to the movements of the pistons and connecting rods in aradial engine, or to resultants of the torque forces; (4) forces due tothe engine unit weight, which puts the upper members' of the presenttype of mounting framework in tension and the lower .members incompression.

The only way to cushion a force is to provide cushioning movement toabsorb the force, and this cushioning movement in an airplane, must besuch as not to create any new forces, or the final results may be as badas or worse than the original forces.

10 In present engine mountings an almost rigid 15 for this is that, ifmore movement were permitted, this cushioning movement would create newforces that would be worse than the original forces if left uncushioned.

The facts regarding the four above mentioned sets of forces are asfollows:

1st. The draft force-If there were no transverse forces operating, thedraft of the propeller would perhaps come equally on all four enginemount connections with the fuselage. But this actually can never occur.

In a radial engine, the torque forces, the movements of the connectingrods and of the pistons, v the presence of out of balance in thepropeller onother moving parts, or one blade 'of the prorpellerpullingmore than another, will result in transverse forces and will create acondition "which will tend to swing the engine in a small circle orother o'rbit. As this slight swinging or I gyratorymovement takes placethe actual, in-

stantly acting draft connection changes, in step with the swingingmovements, so that each of the four connections of the engine mount withthe fuselage, in turn is the actual momentary draft connection.

40 So the draft on the plane is not a steady pull but is a pull whichtravels about the four draft connections in step with the slightgyratory or swinging movement of the engine due to the transverse forcesmentioned. This continual movement of the effective draft connectionproduces a jerky pull or draft upon the plane which can only result invibration in the plane. So, though the actual pull of the propeller maybe steady, the action of the transverse forces upon the draft force,results in an actual vibrational pull or draft force upon the airplane.

To illustrate: In a certain well known nine cylinder 1000 horse powerradial engine, the vibratory force due to connecting rod movements at aspeed of 2160 revolutions per minute, is 1500 pounds. When this 1500pound-transverse force is momentarily acting in the plane of twodiagonally opposite tubular members of the engine mount framework, oneof these diagonally opposite members is subjected to compression and theother diagonally opposite member is subjected to tension.

Thus, for this combination of draft force and transverse force, the moretransverse cushioning movement permitted in present type mountings, thegreater would be the result upon the draft force and the greater wouldbe the vibration due to shifting of the actual momentary draftconnection. That is, new forces would be created.

In my invention, this movement of the draft connection and the resultingvibration, is overcome by a single centrally located resilient draftconnection, which provides steady and non-vibrating pull or draft uponthe plane, in spite of all transverse cushioning movements of the engineunit.

2nd. The torque forces-In the above mentioned 1000 horse power engineeach cylinder is more than six inches in both bore and stroke, and eachcylinder develops a maximum of 111 horse power.

So, when such a cylinder flres, there is a great torque shock, tendingto oscillate the engine in a direction opposite to the direction ofrotation of the propeller.

The only way this torque shock can be cushioned is by torque cushioningoscillation. But, this torque cushioning oscillation must take placewithout creating any new forces.

The rotation of a perfectly balanced mrwheel can take place without thecreation of any new forces; but if the flywheel is unbalanced therotation of the flywheel will create tremendous new forces. a

This holds just as true about the oscillation of a balanced flywheel; itcan take place without the creation of any new forces. And likewise, theoscillation of an unbalanced flywheel will create new forces. But, in aflywheel, the weight only, has to be considered. In a balanced flywheel,the axis passes through the center of mass of the flywheel, and this isenough to avoid the creation of any new forces.

But, in a radial engine, this is not enough. Not only the center of massmust be considered, but also the propeller, and the draft connectionbetween the engine unit and the plane.

So, inmy engine mounting for airplane engines, the axis is so locatedthat it passes through the center of the propeller hub, through thecenter of mass of the engine unit, and through the single draftconnection of the engine unit with the plane.

That is, in my invention torque cushioning oscillation of suificientamplitude is accomplished without movement of the propeller, the centerof mass, or the draft connection with the plane, by so mounting theengine unit as to provide and maintain an axis of oscillation thatpasses through the center of the propeller hub, through the center ofmass of the engine unit, and through the single, centrally located draftconnection. When this is done, sufllcient torque cushioning oscillationmay be provided to properly cushion the torque jerks of the bigcylinders and without creating any new forces from any cause whatever,because of the above mentioned location of the axis of oscillation.

In present radial engine mountings, the lower members of the mountframework are in compression, even if a slight mount of rubber isemployed there is nothing in the construction to locate and maintain anyparticular position for an axis of oscillation, and if any slightoscillation does take place the axis for this oscillation is probably ator near the level of the lower members of the mount framework, whichwould locate the propeller hub and the center of mass considerably abovesuch an axis.

Thus, in present type mountings, the greater the amplitude permitted intorque cushioning oscillation, the greater will be the forces createddue to unbalance of the oscillation both as regards the center of massand as regards the center of the propeller hub.

Ample torque cushioning oscillation with present radial engine mountingswould be like oscillating a flywheel with an off-center shaft.

For this reason, present radial engine mountings are and must besubstantially rigid.

Also, any oscillation with present mountings, slight touch it may be,can not take place about an axis passing through the draft connectionwith the plane, since the actual draft connection, as explained above,revolves about the four points of attachment with the plane, as theengine swings or gyrates, in answer to the transverse forces.

My axis through the center of the propeller hub, through the center ofmass and through the single draft connection, is the only solution thatwill permit the proper and necessary amount of torque cushioningoscillation without creating new and very destructive forces.

Oscillation that would move the propeller hub, the center of mass or thedraft connection, with respect to the engine unit, would create new anddestructive forces.

Thus in the present type of radial engine mountings, the more torquecushioning oscillation permitted the greater would be the vibration dueto the off center position of the propeller, the center of mass and thedraft connection, which in present type mountings is not stationary.

That is, in present type mountings, if ample torque cushioningoscillation were permitted, new forces would be created.

3rd. Transverse jorces.--These forces as mentionedabove, combine withthe draft force, to provide a jerky, rotating, four point draftconnection between the engine unit and the fuselage, one point at a timebeing the momentary, main, draft connection.

These transverse forces, in the present type of radial engine mounting,tend to put tension successively on each of the four points ofattachment with the fuselage and to add to the draft force at one pointwhile tending to put the diiagonally opposite frame member in compresson.

If the engine unit were in perfect running balance and had no transverseforces and were mounted to oscillate about a longitudinal axis passingthrough the center of the propeller hub and through the center of mass,a single central draft connection might not be needed and might givelittle benefit if used. But, as a matter of fact, no engine is inperfect running balance, and all engines have transverse forces. So, mysingle central draft connection is necessary, if a vibrationless draftforce is to be delivered to the plane. Suppose we now consider another.condition with the crankshaft. say, slightly out of balance; this willchange the actual location of the cenance with respect to this new axis,this also will change the location of the center of mass, when forcecushioning oscillation is under consideration, and again the engine willoscillate in perfect balance about the new axis passing through the newlocation of the center of mass, if the mounting is such as to permitsufficient freedom of movement so that this may be accomplished.

But, neither of these conditions can be fulfilled, if the engine ismounted at four points on the fuselage.

In my invention, the mounting includes one rear, central, resilientmounting on the fuselage, so that the transverse cushioning movementspermitted the engine to cushion the transverse forces may take placewithout creating any new forces.

So, the same single, central, attachment principle which permits asteady non-vibrating draft, also permits the transverse cushioningmovements of the engine unit about a single central rear mountingwithout creating any new forces, by such movements.

In some cases the rear mounting may also act as the single central draftconnection, but I do not favor this for the really large engine. v

Thus with transverse forces, if enough cushioning movement is provided,new forces will be created due to the four point connection in presenttype mountings, with the firewall. These forcesf are independent of thedraft force, but when they are combined with the draft force the resultsare very much greater.

Thus, in present mountings increase of transverse cushioning movementscreates new forces.

4th. Weight Iorces.-In present mountings the weight of the engine iscarried by the framework with part of the members in tension and part ofthe members in compression. This puts the engine weight entirely out ofbalance and very top-heavy, as far as any torque cushioning oscillationis concerned, as was explained above under Torque Forces. Since theweight is not located so that it can remain unmoved during engineoscillation, the weight forces would generate new forces if ampleoscillation were permitted to properly cushion the torque forces.

It may be that some of the above mentioned four sets of forces tend tooverlap; but it is thought the above explanation will at least make thematter clear to any mechanic versed in this art.

At any rate it is now clear that in present radial engine mountingscushioning movements of any kind will tend to create new forces whichvery possibly might be more destructive than the original forces.

Thus in present type mountings, every attempt to provide a. really amplecushioning movement for any force has had to be abandoned, and this hasresulted in mountings whose cushioning movements are so slight as toamount to substantially rigid mountings.

In my invention I provide a rearward extension for the engine, (whichmay be designed either as an integral part of the engine, or as anattachment to the engine, as shown in the drawings) and locate theengine partly by the rear mounting, which is located at the rear end of.this extension, and partly by the front mounting which is locatedadjacent the rear of the engine proper, so that the engine weight iscarried at two longitudinally separated points.

If the weight distribution of engine and accessories remains the same asat present, the rear mounting point will carry a negative load, and thefront mounting point will carry more than the weight of the engine, inload.

Though it is possible to redistribute engine and accessory weights sothe rear mounting will carry a positive load, it will generally be foundto be unnecessary. The two mountings locate and maintain the proper axisof oscillation, which passes through the center of the hub of thepropeller, through the center of massof the engine unit (even ifredistribution of weight is required for this), and through the singlecentral draft connection between the engine unit and the fuselage.

When the propeller is geared, it is sometimes offset from thecrankshaft, in which case a redistribution of engine or accessoryweights may be necessary in order to locate the center of mass on theaxis.

My engine unit consists of the propeller, the engine, and accessories,and the rearward extension which carries the rear mounting.

All necessary controls and connections are to be so constructed andarranged as to permit all of the engine cushioning movements withoutfailure in their functions.

What takes place in my method of cushioning out of balance or transverseforces, can perhaps best be illustrated by reference to a boys woodentop. When new, if properly made, the top will spin in perfect balanceabout what may be called its geometric axis. It should be noted that thetop has but one mounting, the rear mounting, where the peg is centeredon the ground, but the top finds its own axis because its upper end,where all the weight is, is free to move transversely. It finds the axiswhich passes through its center of mass.

If a chip is split from one side of the top, the center of mass will beshifted away from where the chip was taken. Then when the top spins, itwill spin about an axis that passes through this new center of mass, andthe former axis that was called the geometric axis, will then revolveabout this new axis. The top will appear to wobble, but except for windresistance, it will be as perfectly balanced as before, because it isfree to find this new axis and revolve about it.

In my mounting I provide a comparatively unloaded and comparativelystationary rear mounting, and a front mounting which carries most of theweight and provides most of the transverse cushioning movements.

By this construction, the engine is comparatively free to find its ownaxis and revolve and oscillate about it in much the same'manner as inthe case of the top above mentioned.

The front mounting consists in metal mounting means adjacent the rear ofthe engine so constructed and arranged as to locate the axis ofoscillation to pass through the center of the rear mounting, through thecenter of mass of the engine unit and through the center of the hub ofthe propeller. This metal mounting means may be a plain metal hearing,or any type or kind of anti-friction bearing, or may be an outer metaltrack co-operating with a series of antifriction bearings mounted on thenine engine bolts on the 23% inch diameter bolt circle, or may be aninner track co-operating with a series of anti-friction bearingsproperly supported, all of which will be clearly understood by anymechanic versed in this art.

For, whatever the kind of type of metal bearing means employed, theresult will be the same in that the center of this front metal bearingmeans positively locates the axis of oscillation in the plane of thisbearing means. That is, regardless of what else takes place, anyoscillation that takes place must take place about the axis located bythis metal bearing means and the rear mounting on the fuselage and thesetwo mountings are so constructed and arranged as to make said axis passthrough the center of mass and the center of the hub of the propeller.Since for smaller engines the rear mounting also may act as the singlecentral draft connection, this axis will also be located to pass throughthe center of the single central draft connection.

The front metal mounting means, of whatever construction, is carried bya proper rubber cushion or other proper resilient means, to provide forthe proper cushioning of all transverse forces and for theself-centering action mentioned above.

This front mounting cushion means, of whatever construction, is properlycarried in a framework similar to the present engine mount, and attachedin a similar manner to the fuselage directly in front of the firewall.

In my construction the rear mounting carries much less weight than thefront mounting since it is more remote from the engine cylinders and thecenter of mass. I

This construction permits the same kind of self-centering action forperfect balance, as illustrated above in connection with a boys top.There is however, this diiference; the top has only rotation; the enginehas both rotation and oscillation, but the self centering will takeplace in the engine very much like it takes place in the top.

The details of construction of my invention, will be better understoodby reference to the drawings, in which- Figure 1 is a side view inpartial section, of my engine mounting, and with some of the co-actingparts of the plane, and with the engine and propeller indicated.

Figure 2 is a front view looking toward the airplane, of the main partsof my mounting shown in Figure 1, for supporting the engine unit uponthe airplane.

Figure 3 is a view of Figure 2, as seen from above.

Figure 4 is an end view of the engine outrigger and rear support, asseen when looking from the rear toward the front.

Figure 5 is a view of Figure 4 as seen from above.

Figure 6 is an enlarged partial sectional View bolted to the ring of therear engine support shown in Figures 4 and 5.

Figure 7 is a sectional view of the outer ball race of the frontmounting.

Figure 8 is a side view of Figure 7.

Figure 9 is an end view oi the rear mounting thrust plate.

Figure 10 is a sectional view of Figure 9.

Figure 11 is a view in partial section of a modified form of the rearframework to carry the rearengine support.

Figure 12 is a detail showing a modified form of connection of the frontframework and of the rear framework to the fuselage, adjacent thefirewall.

Figure 13 is a modified form of connection of the front framework and ofthe rear framework with the fuselage, adjacent the firewall.

Figure 14 is a modified form of connection between the front frameworkand the rear framework.

Figure 15 is a fragmentary detail showing a modified form ofconstruction of the inner ball race of the front mounting and the frontoutrigger ring.

The engine outrigger or extension, is provided with an inner ball race2, which is provided with nine engine fitting bolt holes I, for securelybolting the outrigger to the rear of the engine by the same bolts whichin present engine mountings mount the engine upon the framework that iscarried upon the front end of the fuselage.

The ring 2 has securely welded to it, with proper gussets andreinforcements, the tubular members 4.

The ring 20 is properly welded to and supported by the tubular ring I9.The outer ball race 2! is placed about the inner ball race 2 before theoutrigger is bolted to the engine, and the notches 26 of the two racesare made to register with each other. The balls 22 are then fitted inbetween the two ball races, through the registered notches and when theballs are all in place the outer race is turned degrees so that thenotches 26 will no longer register with each other, which prevents anyof the balls from getting out of place from between the races.

The ball race rubber cushion 23, and. the retainer ring 24 are then putinto place about the outer ball race 2!, and the outrigger is thenproperly bolted to the engine.

The rear rubbers 9 are put into place between the abutments i4 and theend plates I2 and ii of the rear frame ring II.

The engine unit is then ready to be mounted in its frame work.

The ring 5 and its abutments 6 are located to slide in between therubber cushions 9, while the ball bearing rubber cushion 23 slides intothe ring 20. The retainer ring 24 is then properly 20 and the tubularring it, thus clamping the rubber cushion 23 in place, and the thrustplate In is properly attached and locked to the ring 5, thus clampingthe rubbers 9 in place.

The entire engine unit and its framework may now be properly attached tothe airplane at its four clevises Hi, the four pins or bolts passingthrough the clevises l6 and the airplane yokes just in front of thefirewall 25. In some cases rubber bushings may be used for the pins orbolts.

In the mounting thus far described, it will be seen that the rearrubbers 9 combine with the rest of the rear mounting construction topro- Vida or permit universal movement, to resiliently transmit theentire draft of the engine unit to the plane and to resiliently opposetorque cushioning oscillation about the axis which passes through thecenter of the single draft connection, through the center of the frontmounting, through the center of mass of the engine unit, and through thecenter of the hub of the propeller; while the front mounting maintainsthe axis in its proper location and provides ample transverse cushioningfor the transverse forces.

It should be especially noticed that in' order to' have all the drafttaken at the rear single central draft connection, the retainer ring 24should have the proper slight amount of clearance with the rubbercushion 23, though this is not clearly shown in the drawings.

For planes with comparatively small engines the mounting thus fardescribed may be in most cases sumcient; that is, the entire draft andthe entire torque is taken through the rubbers 9 of the rear mounting.

The draft will be delivered through the thrust plate H) to the rubbermembers 9 and to the rear frame ring II.

when the transverse forces are cushioned by 'the cushion ring 23,causing transverse gyrations of the engine, still the draft will beunchanged, and will be transmitted to the plane through the rubbers 9 ofthe single central draft connection provided by the rear mounting.

But, while the transverse and draft forces are thus being properlycushioned, each time a cylinder fires there is .a torque force.

This torque force will tend to oscillate the engine unit about the axisprovided by the front and the rear mountings, and this oscillation willbe resiliently opposed by the rubbercushions 9 co-operating with theabutments 6 of the rear engine ring 5 and with the abutments ll of therear frame ring But since this oscillation takes place about the axisprovided by the two mountings, its amplitude is of little consequence,so long as it is suflicient to properly cushion the torque shock, and solong as all engine controls and connections are properly designed andbuilt to permit such oscillations and transverse cushioning movementswithout altering their actions. That is, all engine unit controls andconnections are to be so constructed and arranged as to permit allengine unit movements without change in the performance of said controlsand connections, as any mechanic versed in the art will understand,

Since the torque cushioning oscillation takes place about an axispassing through the single draft connection, through the center of mass,and through the center of the propeller hub, no new forces whatever willbe created by this oscillation.

It should be noted that the entire engine unit and framework may beremoved from the plane exactly as is the case with present typemountings; that is, simply by the removal of the four clevis bolts justin front of the firewall.

It should also be noted that if desired, removal of the bolts of thethrust plate l0 and of the bolts of the retaining ring 24 will permitthe engine unit to be removed from the engine supporting framework,leaving the engine supporting framework attached to the plane.

It should also be noted that removal of the nine engine bolts whichattach the outrigger to the engine, will permit the engine to be removedfrom the Outrigger, and from the plane.

In case the mounting is used for a large and powerful engine, a slightaddition may be made to properly insure taking care of the draft and thetorque forces without too great cushioning movements. 7

The aligned rings 3|) are properly attached to the outrigger frameworkby welded gussets and reinforcements.

The rings 30 receive the engine draft wrist pin 3|, which is held in thetwo rings 30 by the bolts and nuts 32.

The plane draft wrist pin 33 is properly held in place in rings that aregusseted and reinforced in the plane framework as indicated at 34, orotherwise.

The wrist pin 33 is.held in place by the bolts and nuts 32, similar tothose holding the wrist pin 3| in place.

The construction supporting the wrist pins 3| and 33 are to be strongenough and properly supported, to stand the strains they have to meet,as any mechanic versed in the art'will understand.

It will be notedthat the axes of the wrist pins 3| and 33 cross the axisA- -A at right angles to each other. The draft and torque spring 35, hasan eye at each end supplied with a rubber bushing 36, whose thicknessand consistency will determine the amount of resilience in the draftconnection. This spring 35 is twisted degrees, so that its ends may bereceived by the wrist pins 3| and 33.

The pivotal movements at the wrist pins, the cushioning of the rubberbushings, and the twist of the spring 35, combine to make certain thatno uncushioned vibration may be transmitted by the spring 35 from theengine unit to the airplane. This construction acts to reinforce thesingle draft connection and the resilient torque opposition of the rearmounting.

Though the width and thickness of the spring 35 should, of course, bedesigned forthe particular engine served, it may be from an eighth tothree eighth of an inch thick, and from three to six inches wide andtwenty or more inches long. But, in any case, the spring should bedesigned and built to transmit the draft and the torque with certaintyand safety and still permit as much cushioning of the draft and of thetorque as is required. It should be noted that the draft and torquespring 35 combines with, or reinforces the rear mounting of the engineunit, to transmit both the draft and the torque forces resiliently fromthe engine unit to the plane.

Figure 11 illustrates a modified form for the support upon the airplane,of the rear mounting of the engine unit.

The flange of the firewall plate 25' may be bolted to either the frontor the rear face of the firewall proper. It is supported in the rearframe ring II, which in turn is properly supported by the tubularframework members l5, or otherwise. The front plate I2 is properlybolted to the firewall plate 25' and to the rear frame ring II.

This separate firewall plate may, of course, be used in the Figure 1construction, if desired, either with or without the spring 35.

When the engine unit isremoved from the airplane with this rear mountingsupport construction, the front plate I2 is removed in any case, whetherthe front framework is left attached to the plane or not, and the frontframework may be removed from the plane by removal of the four clevispins, or the engine may be removed from the front framework by removalof the retainer ring 24; or the engine alone may be removed by removalof the nine engine bolts which attach the outrigger to the engine. Forlarge engines a draft and torque spring should be used with this rearmounting.

Figure 12 is a modified form of construction by which the frontframework and the rear framework may be Joined together detachably,instead of permanently.

The front framework clevis ll is straddled by the rear framework clevis4|, and the same long clevis pin passes through both clevises and theairplane framework yoke.

In Figure 13 still another modified form of mounting the front and therear framework is shown. The front framework clevis I. is mounted on itsyoke by its pin in the usual way, and the rear framework clevis 4| ismounted on the airplane framework and yoke by an entirely separateclevis and clevis pin.

Figure 14 shows a modified form for Joining the front and the rearframework detachably instead of permanently. 1

The clevis 42 is Joined by the pin 43 with the clevis yoke 44 of thefront framework, and the clevis i6 of the front framework is mounted inthe usual way upon the airplane framework and yoke.

Figure 15 shows a modified form of constructionfor the inner ball raceand front ring of the outrigger.

The inner race 2' is made entirely separate from the ring 50. The ringSI has a flange which acts to clamp the race 2 against the engine.

In this construction the inner ball race may easily be replaced whenworn without the necessity of replacing the front ring of the outrigger.

It will now be seen that my invention consists in a construction inwhich the draft connection means of the engine with the plane is at asingle point, remote from the cylinder portion of the engine.

This draft connection means may be at the rear of an outrigger, asshown, or the engine and accessories may be designed to extend the rearof the engine and take the place of the outrigger.

The essential point is that whatever the details of construction, therear resilient mounting of the engine unit, which acts as the draftconnection means of the engine unit with the plane, should be spacedconsiderably to the rear ofthe engine ucylinders.

The draft connection means may be attached to the plane to the rear ofthe plane of the pres ent firewall as shown; or it may be right at thefirewall line, or if desired may even be in front of the firewall.

But, however these details are constructed, the draft connections meansshould also include resilient means acting to support positive ornegative load and to resiliently oppose the torque cushioningoscillation of the engine unit, while at the same time permitting anyand all force cushioning movements of the engine unit, without movementof the point of draft of the engine with the plane.

Any other set of details of construction than those shown for properlysupporting the front engine mounting upon the plane and permitting forcecushioning movements in any direction may be employed, so long as thetorque cushioning oscillation takes place about the axis of oscillationpassing through the center of the propeller hub, the center of mass, andthe draft connection.

Thus the pull of the engine on the plane will be steady and acting uponone point,'and yet through resilient means, the torque forces may becushioned by plenty of torque cushioning oscillation without creatingany new forces, and the transverse forces may be cushioned by transversecushioning movements without transmitting such movements to the plane orcreating any new forces.

Naturally there are many changes that can be made in my inventionwithout departing from the essence thereof, which consists of aresilient, single, central, draft connection means between the engineunit and the plane, and engine supporting means supporting the engine onthe plane and permitting all necessary force cushioning movements aboutthe draft connection or about the axis passing through the draftconnection as a center, whether the resilient draft and the resilienttorque connections between some part of the engine unit and some part ofthe plane are entirely of rubber or are of rubber and steel.

Thus it will be seen every force that might be transmitted from theengine unit to the plane, can, in my mounting, only be transmittedthrough resilient members, and the construction is such that thecushioning movements can be so calibrated or designed into theconstruction as to provide such cushioning for every engine force thatthe senses will not be able to perceive them; and these cushioningmovements, will none of them create new forces.

It will be appreciated by anyone versed in the art that many variationsare possible in the construction details of the particular structuresillustrated, and that various slight changes may also be made in mymethod without departing from the essence thereof.

It will also be appreciated, that though my invention has been describedmainly in connection with a nine cylinder radial-engine, it will operateequally well with a seven cylinder of a double row fourteen cylinderradial, or any other kind, type, or construction of engine, if the sametheories and understanding were employed by a competent mechanic versedin the art.

This description deals especially with airplane engines with thepropeller in front, but is Just as true if the engine were mounted in aZeppelin. Any any mechanic versed in the art will understand that themethod, the principles and even the details of construction will applyequally well in Zeppelin or airplane engines with the propellers to therear of the engines, with only such necessary changes as a mechanic willreadily understand. So, I do not wish to be limited to the exactillustrations and description made herein, but what I claim as new anddesire to protect by Letters Patent, is as follows:

1. In an airplane engine and propeller unit mounting, movable draftconnection means between the said unit and the plane, spaced remotelyfrom the cylinder portion of the engine unit, and compound supportingmeans longitudinally spaced toward the engine cylinders from said draftconnection means, said compound supporting means comprising resilientlymounted rotary bearing means for resiliently supporting the said unit onthe plane for continual, permarubber elements fitting intolongitudinally extending grooves in a means carried by said engine.

2. In an airplane engine and propeller unit mounting, movable draftconnection means between the said unit and the plane, spaced remotelyfrom the cylinder portion or the engine unit, and compound supportingmeans longitudinally spaced toward the engine cylinders from said draftconnection means, said compound supporting means comprising resilientlymounted rotary bearing means for resiliently supporting the said unit onthe plane for continual, permanent oscillatory movement about an axisand; combining with said draft connection means to provide a single axisof oscillation about which said unit may oscillate in balance at alltimes and under all conditions, and a torque member composed of alongitudinally extending leaf steel spring movably connected at one endto the engine and at the other end to the airplane.

3. In a mounting for an airplane engine and propeller unit, an extensionacting as a part oi! the engine to form a unit therewith and extending.substantially concentric with the engine crankshaft, mounting meansattaching the end or said extension remote from the engine to theairplane and providing a single movable connection means and providingfor resiliently opposed movements between airplane in any direction,jacent the other end of the extension and supporting the said unit onthe airplane and providing for cushioning movements in any direction andincluding oscillatory, axis-locating means, said mounting meanscombining resiliently mounted rotary bearing means to provide for andmaintain a single axis of oscillation about which the engine andpropeller unit may oscillate in balance at all times, and said mountingmeans remote from the engine being provided with a series oflongitudinally extending grooves, a series or rubber elements fitting insaid grooves, and said elements surrounded by and received in a seriesof longitudinal grooves provided by a mounting element carried by saidairplane.

4. In a mounting for an airplane engine and propeller unit, an extensionacting as a part of the engine to form a unit therewith and extendingsubstantially concentric with the engine crankshaft, mounting meansattaching the end of said extension remote from the engine to theairplane and providing a single movable connection means and providingfor resiliently opposed movements between the extension and the airplanein any direction, mounting means adjacent the other end of saidextension and supporting the said unit on the airplane and providing forcushioning movements in any direction and including oscillatory,axis-locating means, said mounting means combining resiliently mountedrotary bearing means to provide for and maintain a single axis ofoscillation about which the engine and propeller unit may oscillate inbalance at all times, and a torque member composed oil a longitudinallyextending leai steel spring movably connected atone end to the engineand at the other end to the airplane.

' ROI-LAND S. TRO'I'I.

the extension and themounting means ad-

